Tube couplings are used to connect flexible tubes in numerous fluid power and control systems. Each of the tubes require couplings to connect the ends of the tube to bodies which, for example, may be conventional fittings, valves, manifolds or similar devices for transmitting and receiving pressurized air. In the past, connecting and disconnecting tubes was a time-consuming and therefore expensive task frequently performed in the field where specialized tools may not have been readily available. To solve this problem a wide variety of "push-to-connect" type couplings have been developed which permit a tube to be quickly and easily connected or disconnected without the use of tools. With these couplings, a tube is connected by simply press-fitting a coupling into a bore and then inserting the leading end of the tube into the coupling. Typically, the coupling contains a plurality of components which releasably or permanently retain the tube therein.
Quick-connect couplings are widely used in the trucking industry for fittings in and on cabs, so that pressurized air in the cab can be transmitted for numerous purposes. Fittings used outside of the cab on the chassis of the cab are subject to environmental degradation due to dirt, grime, moisture and atmospheric conditions which are not present within the passenger compartment of the cab. To date, failure of these fittings in the field has not occurred; however, there is a need to address this concern by improving the fittings so that the effects of adverse environment conditions are minimized, thus minimizing the risk of failures in the future.